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For what value of c are the three points (-3,1), (5,5), and (6,c) on the same line?

Feb 16, 2020

#1
0

hint:

use slope formula.

Make sure all the points have the same slope

Feb 16, 2020
#4
0

I put 19 but it was wrong...

Guest Feb 16, 2020
#7
+1

Then you probably did it wrong.

AnimalMaster  Feb 17, 2020
#1
0

The slope between the points (-3,1) and (5,5) is 8/4 = 2.  Then by point-slope form, the equation of the line is y - 1 = 2(x + 3), or y = 2x + 7.  So when x = 6, c = 2*6 + 7 = 19.

Guest Feb 16, 2020
#4
0

I put 19 but it was wrong...

Guest Feb 16, 2020
#7
+1

Then you probably did it wrong.

AnimalMaster  Feb 17, 2020
#3
0

Just to check, 4.916722 is the right answer, right?

Feb 16, 2020
#6
0

nevermind. 5.5

IONJigZz  Feb 17, 2020
#8
+2

For what value of c are the three points (-3,1), (5,5), and (6,c) on the same line?

$$\begin{array}{|rcll|} \hline \dfrac{c-5}{6-5} &=& \dfrac{5-1}{5-(-3)} \\\\ c-5 &=& \dfrac{4}{8} \\\\ c-5 &=& \dfrac{1}{2} \\\\ c &=& 5+ \dfrac{1}{2} \\\\ \mathbf{c} &=& \mathbf{5.5} \\ \hline \end{array}$$ Feb 17, 2020